"Altitude Sickness" refers to the group of illnesses due to exposure to high altitude, especially those consequent to exposure to reduced oxygen pressure, (hypobaric hypoxia). The incidence and severity of illness increases with altitude and the symptoms largely reflect the various organs' response to inadequate oxygen supply. The main systems affected are the lungs and the brain.

What are the main types of Altitude Sickness?

The commonest form is known as Acute Mountain Sickness, AMS, which is usually a benign illness occurring at altitudes beyond 2000 - 2500 meters. This is characterized by headache, insomnia, tiredness and mild shortness of breath and is generally self limiting, acclimatization occurring in 2-5 days with resolution of symptoms. AMS occurs in about 40% of individuals ascending rapidly to 3000m and 75% of those rapidly ascending to 4500m.

Severe forms of altitude sickness occurs at higher altitudes. High Altitude Cerebral Oedema, HACE, occurs in 1-2% of short term travellers to 3-5000m and is characterized by progressive cerebral dysfunction, ataxia, confusion and unusual behavior and can lead to coma and death. High Altitude Pulmary Oedema, HAPE, occurs in 2% of climbers to 6000m and is the commonest cause of fatal altitude sickness. Symptoms include shortness of breath, a cough and blood stained sputum.

What are the treatments of Altitude Sickness?

The treatment of all forms of altitude sickness is primarily Rest, Oxygen and Descent. For AMS, rest, fluids and simple analgesics is usually adequate to allow acclimatization. Sedatives should be avoided. Oxygen is occasionally required and descent considered if symptoms persist. Dexamethasone has a role in the treatment of HACE and Nifedipine is used to treat HAPE.

Who gets Altitude Sickness?

Anybody may be at risk of altitude illnesses. Males and females of all ages are equally effected and illness occurs in children as the same in adults. However, symptoms can be harder to recognize in children. General fitness is not a prevention. Having altitude illness previously, is pre-disposing to repeat illness.

Is there prevention for Altitude Sickness?

All travellers to altitude should be warned about the potential for altitude illnesses especially AMS. Rapid ascent increases the risk, so planning itineraries with gentle ascent is helpful. Allow one night for each rise at 500m above 2000m. Drinking plenty of water, avoiding alcohol, high carbohydrate diet and moderate exercise is helpful to assist acclimatisation. Acetazolamide ( Azomid) can be used to speed acclimatisation in some individuals.

Other Problems with Altitude.

Ultra violet injuries,( sunburn), occur as well as cold injuries. Thrombosis of the legs occurs at higher rates. Accidents are more common. Retinopathies can occur at very high altitudes.

Who should not go to Altitude?

The only major medical problems that would severely be compromised by exposure to altitude are individuals with moderate to severe chronic obstructive airway disease, those with congestive cardiac failure, those with pulmonary hypertension and individuals with sickle-cell anemia.

Care should be taken by individuals with epilepsy, underlying arrhythmias or severe sleep-apnoea.

Pregnant woman should not ascend beyond 3500m. Asthma, diabetes, old age or previous cardiac bypass surgery are not contra-indication to going to altitude.